Medical manipulator

ABSTRACT

A medical manipulator comprises a working unit ( 10 ) that performs operations, an operating unit ( 20 ) that generates instructions, a drive unit ( 50 ) that drives the working unit on the basis of instructions given thereto by the operating unit, a power transmission mechanism ( 60 ) for transmitting driving force of the drive unit to the working unit, and a control unit ( 40 ) for controlling the power transmission mechanism on the basis of instructions given thereto by the operating unit. The power transmission mechanism includes a first power transmission unit ( 61 ) interlocked with the drive unit, and a second power transmission unit ( 63 ) interlocked with the working unit and capable of being detachably connected to the first power transmission unit. A back drive torque of the first power transmission unit is larger than a back drive torque of the second power transmission unit.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.10/661,636, filed on Sep. 15, 2003, now U.S. Pat. No. 6,994,716. Thisapplication is further based upon and claims the benefit of priorityfrom the prior Japanese Patent Application No. 2002-271947, filed onSep. 18, 2002; the entire contents of which are incorporated herein byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a medical manipulator and, moreparticularly, to a medical manipulator having a simple mechanism andexcellent in operability and safety.

2. Description of the Related Art

Referring to FIG. 13, laparoscopic cholecystectomy forms three smallincisions 151, 152 and 153 in the abdominal wall, fits tracheal tubes154 in the incisions 151, 152 and 153, inserts an endoscope 161, andforceps 171 and 172 through the tracheal tubes 154 into the abdomen. Anoperator 160, usually, a surgeon, conducts an operation, watching animage taken by the endoscope 161 and displayed on the screen of amonitor 162. Laparoscopic cholecystectomy reduces physical load on thesubject and reduces the number of days for which the convalescentpatient is obliged to stay in the hospital before leaving the hospitalbecause laparoscopic cholecystectomy does not need to incise theabdominal wall. The field to which such a surgical operation isapplicable is expected to expand.

Studies have been made for the development of techniques relating toremote-controlled robots, such as master-slave manipulators, to beapplied to the medical field, and some techniques have been applied toclinical purposes (http://www.computermotion.com,http://www.intuitivesurgical.com). Techniques relating toremote-controlled robots provide a master-slave manipulator systemincluding a master arm to be operated by an operator, and a slave armfor actually treating a diseased part, completely separated from themaster arm. Electric signals corresponding to instructions given byoperating the master arm are transmitted to the slave arm. Usually, themaster arm and the slave arm are articulated arms having at least sixdegrees of freedom of motion. The master-slave manipulator system is acomplicated system including a controller for controlling the joints ofthe articulated arms, an electrical control system, and many partsincluding wiring lines.

The inventors of the present invention proposed previously a simplemedical manipulator (robotic forceps) developed by applying robottechniques to a conventional pair of forceps as shown in FIG. 14 inJP2000-350735A (Patent document 1). Referring to FIG. 14, thispreviously proposed medical manipulator comprises a control unit 20including a position controller 23 and an operation controller 24, aconnecting unit 30 having one end connected to control unit 20, aworking unit 10 connected to the other end of the connecting unit 30 andincluding support devices 15 and 16 supporting an end effector havingoperating members 14 for motions with at least two degrees of freedom,and a controller, not shown, for changing the positions of the operatingmembers 14 of the end effector by controlling the support devices 15 and16 according to instructions given by the position controller 23 andoperating the operating members 14 of the end effector according toinstructions given by the operation controller 24.

The inventors of the present invention proposed previously a medicalmanipulator as shown in FIG. 15 having degrees of freedom of motionsuitable for suture and ligation in JP2002-102248A (Patent document 2).This medical manipulator comprises a working unit 10, a control unit 20,and a connecting unit 30 having opposite ends respectively connected tothe working unit 10 and the control unit 20. The working unit 10includes a support device capable of turning about a first axis 11perpendicular to the axis 31 of the connecting unit 30, and a secondaxis perpendicular to the first axis 11, and an end effector fortreating a diseased part. The end effector has a gripper 14 is capableof turning about an axis substantially parallel to the second axis 12.The working unit 10 has a pitching joint 15 and a rolling joint 16 formoving the gripper 14 with two degrees of freedom. The control unit 20includes a position controller 23 capable of turning about a third axis21 perpendicular to the axis 31 of the connecting unit 30 and a fourthaxis 22 perpendicular to the third axis 21, and an operation controller24 to be operated by an operator. The operator grips the operationcontroller 24. The wrist of the operator gripping the operationcontroller 24 turns about an axis substantially parallel to the fourthaxis 22. The gripping motion of the gripper 14 for treating a diseasedpart is controlled by operating the operation controller 24.

This previously proposed medical manipulator, differing from theremote-controlled master-slave manipulator, is formed by connecting thecontrol unit (master unit) and the working unit, i.e., hand or forceps(slave unit) by the connecting unit, and is capable of achieving bothsimple, reliable, quick, large operations that can be performed by theoperator, which is an advantage of the conventional forceps, anddelicate, difficult operations and operations from difficult directions,which is an advantage of the manipulator. Since the working unit isprovided with joints for bending and turning motions, the position ofthe end effector can freely be adjusted. Therefore, suturing andligating operations from various directions, which have been difficultfor the conventional forceps to perform, can easily be performed. Theoperator is able to use the medical manipulator and the conventionalforceps simultaneously by operating the medical manipulator by the righthand and operating the forceps by the left hand. The simple, compactmedical manipulator is inexpensive.

Medical instruments, particularly, surgical instruments, as well asmedical robots, cannot be used for surgical operations unless thoseinstruments are sterilized and cleaned. Generally, the working parts ofmedical robots, medical devices and surgical instruments are smearedwith the blood and tissues of subjects of operations, and hence need tobe washed clean and to be sterilized. At least the working unit, thatcomes into contact with the subject, of a large device can be removedfrom the main unit or can be separated from the control unit forcleaning and sterilization. Therefore, it is essential that the workingunits of medical robots, medical devices and surgical instruments areseparable from the control units. The working unit separated forsterilization from the control unit must be capable of being combinedwith the control unit at a predetermined position relative to thecontrol unit and in a predetermined orientation relative to the controlunit.

Generally, a robot must be capable of a resetting operation, i.e., aninitializing operation, when the robot is connected to a power source.The initializing operation operates the joints of the robot according toa predetermined sequential procedure to detect the arrival of the jointsat their initial positions by initialization sensors incorporated intothe joints, sets the joints in initial angular positions, and resetsincremental encoders respectively combined with the output shafts ofmotors. It is very troublesome to operate a medical robot forinitialization for returning the medical robot to its initial positionalstate during a surgical operation. Thus, it is desired that such aninitializing operation is avoided as far as possible in a tensesituation of a surgical operation. Therefore, it has been desired todevelop a medical robot that can immediately be used after the same hasbeen connected to a power source without requiring any initializingoperation.

The medical manipulator previously proposed by the inventors of thepresent invention is provided integrally with the master unit and theslave unit, the operator who operates the medical manipulator must bearthe weight of the medical manipulator. Therefore, it is the mostimportant problem to form the medical manipulator in a small,lightweight structure. Therefore, it is very difficult, in respect ofavailable spaces and allowable weight, to combine initialization sensorswith the joints and other necessary parts. Even if initializationsensors could be combined with the joints and other necessary parts, alarge number of wiring lines are necessary for connecting theinitialization sensors to the associated parts and devices, whichincreases the weight of the medical manipulator and deteriorates theoperability of the medical manipulator significantly.

Although a robot capable of always securing an absolute position withoutperforming an initializing operation can be formed by providing therobot with absolute encoders, the absolute encoders are larger and needmore wiring lines than incremental encoders. Thus, the employment ofabsolute encoders is not suitable for the medical manipulator previouslyproposed by the inventors of the present invention.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to solve theforegoing problems in the prior art and to provide a small, lightweight,medical manipulator, excellent in operability, not requiring anyinitializing operation before starting a surgical operation, andincluding a working unit capable of being connected to and disconnectedfrom a drive unit for cleaning and sterilization, and capable of beinginterlocked with the drive unit.

According to the present invention, a medical manipulator comprises: aworking unit that performs operations; an operating unit that generatesinstructions; a drive unit that drives the working unit on the basis ofinstructions given thereto by the operating unit; a power transmissionmechanism for transmitting driving force of the drive unit to theworking unit; and a control unit for controlling the power transmissionmechanism on the basis of instructions given thereto by the operatingunit; wherein the power transmission mechanism includes a first powertransmission unit interlocked with the drive unit, and a second powertransmission unit interlocked with the working unit and capable of beingdetachably connected to the first power transmission unit, and a backdrive torque of the first power transmission unit is larger than a backdrive torque of the second power transmission unit.

In the medical manipulator according to the present invention, thecontrol unit is capable of executing operations specified by a controlprogram for setting the first power transmission unit in a predeterminedinitial positional state at the normal completion of an operation.

In the medical manipulator according to the present invention, thecontrol program waits in a waiting state where the control unit isinitialized by connecting the medical manipulator to a power source foran operation start instruction specifying an operation for setting theoperating unit in an operational state, a return-to-origin instructionspecifying an operation for setting the first power transmission unit inthe predetermined initial positional state or a shutdown instructionspecifying an operation for disconnecting the medical manipulator fromthe power source, and the control program makes the shutdown instructioneffective only when it is confirmed that the first power transmissionunit has been set in the predetermined initial positional state.

The medical manipulator according to the present invention may furthercomprise an initialization detecting means capable of being connected tothe first power transmission unit when the first power transmission unitis disconnected from the second power transmission unit and of detectingcomponents of the first power transmission unit set at predeterminedjoining positions, respectively.

In the medical manipulator according to the present invention, the backdrive torque of the first power transmission unit has a strength morethan 0.05N·m when the first and the second power transmission unit areconnected together.

In the medical manipulator according to the present invention, theworking unit and the second power transmission unit are integrated in anassembly, the operating unit and the first power transmission unit areintegrated in an assembly, and the assembly of the working unit and thesecond power transmission unit, and the assembly of the operating unitand the first power transmission unit can detachably connected together.

In the medical manipulator according to the present invention, theworking unit and the second power transmission unit are integrated in anassembly; and the assembly of the working unit and the second powertransmission unit, the first power transmission unit, and the operatingunit can detachably be connected together.

Since the first power transmission unit and the second powertransmission unit can detachably be connected, and a back drive torqueof the first power transmission unit is larger than a back drive torqueof the second power transmission unit, the working unit can be cleanedand sterilized, a return-to-origin operation can be carried out withoutusing any absolute encoders or origin sensors, and the working unit canalways be set in its initial state before and after connecting theworking unit to and disconnecting the same from the drive unit.

Since the control unit sets the first power transmission unit in thepredetermined initial positional state after the normal completion of anoperation, the medical manipulator can be used immediately after theconnection of the same to the power source without requiring atroublesome return-to-origin operation. Thus, troublesome work in atense situation of surgical operation can be avoided and thereby theefficiency of the surgical operation can remarkably be improved.

Since the initialization detecting means is capable of being detachablyconnected to the first power transmission unit, the initialization ofthe drive unit can be detected without permanently mounting theinitialization detecting means on the first power transmission unit, andthe return-to-origin operation is possible even in a state where theoperation is ended abnormally.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the presentinvention will become more apparent from the following description takenin connection with the accompanying drawings, in which:

FIG. 1 is a schematic perspective view of a medical manipulator in afirst embodiment according to the present invention;

FIG. 2 is a perspective view of the medical manipulator shown in FIG. 1as divided by a first dividing method;

FIG. 3 is a perspective view of the medical manipulator shown in FIG. 1as divided by a second dividing method;

FIG. 4 is a perspective view of the medical manipulator shown in FIG. 1as divided by a third dividing method;

FIG. 5 is a perspective view of an operating unit included in a medicalmanipulator in a second embodiment according to the present inventionprovided with an initialization detecting device;

FIG. 6 is an exploded perspective view of the operating unit shown inFIG. 5;

FIG. 7 is a side elevation of the medical manipulator of assistance inexplaining a power transmission mechanism;

FIG. 8 is a view of assistance in explaining operations for connectingand disconnecting a working unit and a drive unit included in themedical manipulator shown in FIG. 1;

FIG. 9 is a view of assistance in explaining operations for connectingand disconnecting the working unit and the drive unit included in themedical manipulator shown in FIG. 1;

FIG. 10 is a view of assistance in explaining operations for connectingand disconnecting the drive unit;

FIG. 11 is a side elevation of an initialization detector included inthe medical manipulator of the present invention;

FIG. 12 is a flow chart of a procedure for operating the medicalmanipulator of the present invention;

FIG. 13 is a pictorial view of assistance in explaining the use of amedical manipulator;

FIG. 14 is a perspective view of a conventional medical manipulator; and

FIG. 15 is a perspective view of a conventional medical manipulator.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1, a medical manipulator 1 in a first embodimentaccording to the present invention comprises a working unit 10 thatperforms necessary operations, an operating unit 20 for generatinginstructions specifying operations to be performed by the working unit10, a drive unit 50 for driving the working unit 10 on the basis ofinstructions generated by the operating unit 20, a power transmissionmechanism 60 for transmitting the drive force of the drive unit 50 tothe working unit 10, and a control unit 40 for controlling the powertransmission mechanism 50 to make the working unit 10 operate on thebasis of instructions generated by the operating unit 20. The workingunit 10 and the operating unit 20 are connected by a bar-shapedconnecting unit 30. The working unit 10 is disposed at one end of theconnecting unit 30, and the operating unit 20 and the drive unit 50 aredisposed near the other end of the connecting unit 30. The drive unit 50includes three motors. The number of degrees of freedom of motion andthe arrangement of joints do not need to be limited to those shown inFIG. 1.

The power transmission mechanism 60 is interlocked through theconnecting unit 30 with the working unit 10, and is interlocked with thedrive unit 50. The power transmission mechanism 60 includes a firstpower transmission unit 61 interlocked with the drive unit 50, and asecond power transmission unit 63 interlocked with the working unit 10.The first power transmission unit 61 and the second power transmissionunit 63 are engaged detachably to connect the working unit 10 and thedriving unit 50 separably. The power transmission mechanism 60 includesa plurality of power transmitting elements including, for example,links, gears, a wire-pulley mechanism, a reduction gear and couplings.The power transmission mechanism 60 transmits the driving power of thedrive unit 50 including the motors to the working unit 10 by thewire-pulley mechanism disposed in the connecting unit 30 to drive theworking unit 10 for operations including bending operations, turningoperations, gripping operations.

FIG. 2 shows the medical manipulator 1 divided into an assembly of theworking unit 10 and the connecting unit 30 and that of the operatingunit 20 and the drive unit 50. The medical manipulator 1 may be dividedinto an assembly of the working unit 10, the connecting unit 30 and theoperating unit 20, and the drive unit 50 as shown in FIG. 3, may bedivided into an assembly of the working unit 10 and the connecting unit30, the operating unit 20 and the drive unit 50 as shown in FIG. 4. Themedical manipulator 1 will be described on an assumption that workingunit 10 and the drive unit 50 are connected separably as shown in FIG.2.

Referring to FIGS. 2 and 7, the power transmission mechanism 60 has afirst power transmission unit 61 including couplings and interlockedwith the drive unit 50, a power transmitting device 62 includingreduction gears and interposed between the first power transmission unit61 and the drive unit 50; a second power transmission unit 63 includingcouplings and interlocked with the working unit 10; a power transmittingdevice 64 including pulleys connected to the second power transmissionunit 63; a power transmitting device 65 including a wire rope or a rodconnected to the power transmitting device 64; and a power transmittingdevice 66 interlocking the power transmitting device 65 and the workingunit 10 and including pulleys, gears and links. Power can be transmittedfrom the drive unit 50 to the working unit 10 by connecting the firstpower transmission unit 61 including the couplings, and the second powertransmission unit 63 including the couplings. The power transmissionmechanism 60 may be any other suitable combination of power transmittingdevices.

FIG. 8 and FIG. 9 are views of assistance in explaining operations forconnecting and disconnecting the working unit 10 and the drive unit 50of the manipulator 1. The drive unit 50 including three drive motors,and the first power transmission unit 61 are mounted on a base 52. Thesecond power transmission unit 63 and a housing 58 are mounted on a base56. The housing 58 is connected to an end part of the connecting unit30. The power transmitting device 64 is contained in the housing 58.Latching pins 54 connect the bases 52 and 56 separably. The base 52 isseparated from the base 56 to separate the first power transmission unit61 from the second power transmission unit 63. In connecting the firstpower transmission unit 61 and the second power transmission unit 63,the first power transmission unit 61 and the second power transmissionunit 63 are set opposite to each other. Then, the first powertransmission unit 61 adjusts the position of the second powertransmission unit 63 so that the first power transmission unit 61 andthe and the second power transmission unit 63 are connected in the samepositional relationship as a predetermined positional relationship inwhich the first power transmission unit 61 and the second powertransmission unit 63 had been connected before the same were separatedfrom each other. After the first power transmission unit 61 and thesecond power transmission unit 63 have been set in the predeterminedpositional, the bases 52 and 56 are fastened together by the latch pins54. Thus, the medical manipulator 1 can securely set in the initialstate. The first power transmission unit 61 and the second powertransmission unit 63 may be connected and separated by using anysuitable fastening means, such as screws, instead of using the bases 52and 56 and the latch pins 54.

The first power transmission unit 61 and the second power transmissionunit 63 are disconnected after the completion of an operation, such as asurgical operation, to clean and sterilize the working unit 10. Aconnecting procedure for connecting the first power transmission unit 61and the second power transmission unit 63 after the working unit 10 hasbeen cleaned and sterilized will be described. The first powertransmission unit 61 is capable of exerting a back drive torquesufficient for holding the couplings of the first power transmissionunit 61 at positions at which the couplings are located before the firstpower transmission unit 61 and the second power transmission unit 63 aredisconnected after the first power transmission unit 61 and the secondpower transmission unit 63 have been disconnected. The back drive torqueis a torque necessary for transmitting power from the first powertransmission unit 61 to the drive unit 50. The sufficient back drivetorque of the first power transmission unit 61 restrains the couplingsof the first power transmission unit 61 from being moved manually forpositional change.

When the operation of the medical manipulator 1 is completed normally,the control unit 40 sets the first power transmission unit 61 in itsinitial positional state. Therefore, the first power transmission unit61 is in its initial positional state when the working unit 10 isseparated from the drive unit 50 after the operation of the medicalmanipulator 1 has normally been completed. Since the first powertransmission unit 61 has a sufficient back drive torque, the first powertransmission unit 61 remains in the initial positional state until thefirst power transmission unit 61 and the second power transmission unit63 are connected again. Since the back drive torque of the first powertransmission unit 61 has a strength more than 0.05N·m, the first powertransmission unit 61 cannot rotate as long as the drive torque more than0.05N·m is not applied to the outside diameter portion of the firstpower transmission unit 61. Thus, the first power transmission unit 61has the sufficient back drive torque so that the first powertransmission unit 61 restrains the couplings of the first powertransmission unit 61 from being moved manually for positional change.

When the second power transmission unit 63 interlocked with the workingunit 10 is disconnected from the first power transmission unit 61, thecouplings of the second power transmission unit 63 can manually be movedby a relatively low torque. Therefore, the couplings of the second powertransmission unit 63 are not necessarily held, after the working unit 10has been cleaned and sterilized, at positions where the couplings of thesecond power transmission unit 63 were positioned when the second powertransmission unit 63 was disconnected from the first power transmissionunit 61, and it is highly possible that the positions of the couplingsof the second power transmission unit 63 are changed. If the positionsof the couplings of the second power transmission unit 63 are changedafter the second power transmission unit 63 has been disconnected fromthe first power transmission unit 61, the first power transmission unit61 and the second power transmission unit 63 cannot be connected in thesame positional relationship as before. The first power transmissionunit 61 is capable of exerting the sufficiently high back drive torqueand the couplings of the second power transmission unit 63 can be turnedby a relatively low torque. Thus, since a back drive torque of the firstpower transmission unit 61 is larger than a back drive torque of thesecond power transmission unit 63, the couplings of the second powertransmission unit 63 can be turned, when the second power transmissionunit 63 is brought into engagement with the first power transmissionunit 61, by the first power transmission unit 61 to the positions wherethe couplings of the second power transmission unit 63 were positionedand were aligned with the corresponding couplings of the first powertransmission unit 61 when the second power transmission unit 63 wasdisconnected from the first power transmission unit 61.

Since the working unit 10 touches the subject's body directly and issmeared with blood and tissues, the working unit 10 used for a surgicaloperation needs to be disconnected from the drive unit 50 and to becleaned and sterilized. In cleaning the working unit 10, the componentsof the second power transmission unit 63 and the power transmittingdevices 64, 65 and 66 must manually be moved to wash off blood andtissues remaining in gaps in the components of the second powertransmission unit 63 and the power transmitting devices 64, 65 and 66.Therefore, it is usual for the positions of the couplings of the secondpower transmission unit 63 to change from those where the couplings werepositioned when the second power transmission unit 63 was disconnectedfrom the first power transmission unit 61. Since the couplings of thesecond power transmission unit 63 can be moved, as mentioned above, tothe positions where the couplings of the second power transmission unit63 can be joined to those of the first power transmission unit 61 heldat the initial positions after the disconnection of the second powertransmission unit 63 from the first power transmission unit 61, thefirst power transmission unit 61 and the second power transmission unit63 can be connected in the predetermined positional relationship.

Thus, the medical manipulator 1 of the present invention can easily berestored to its initial state after disconnecting the working unit 10from the drive unit 50 and cleaning and sterilizing the working unit 10,even if the positional state of the second power transmission unit 63 ischanged after disconnecting the second power transmission unit 63 fromthe first power transmission unit 61. The medical manipulator 1 may besubjected to a sterilizing process after the same has been cleaned andreassembled.

Thus, the working unit 10 can be set in the predetermined positionalstate in connecting the second power transmission unit 63 to the firstpower transmission unit 61 after disconnecting the working unit 10 fromthe drive unit 50 without using any absolute encoders and originsensors. Thus, the medical manipulator can be formed in a small,lightweight structure and is excellent in operability.

A medical manipulator 1 in a second embodiment according to the presentinvention will be described with reference to FIGS. 5, 6, 10 and 11. Themedical manipulator 1 has a first power transmission unit 61 and asecond power transmission unit 63. As shown in FIGS. 5 and 6, aninitialization detector 70 can be combined with the first powertransmission unit 61. The initialization detector 70 can freely becombined with and separated from the first power transmission unit 61after the first power transmission unit 61 has been disconnected fromthe second power transmission unit 63. The initialization detector 70 iscombined with the first power transmission unit 61 after disconnectingthe first power transmission unit 61 from the second power transmissionunit 63.

Referring to FIGS. 10 and 11, the initialization detector 70 is mountedon a base 76. The initialization detector 70 has couplings 70 asupported on the base 76. The couplings 70 a are engaged with thecouplings of the first power transmission unit 61, and then the base 76is fastened to a base 52 holding the first power transmission unit 61 bylatch pins 54. Subsequently, the motors of a drive unit 50 are actuatedto set the first power transmission unit 61 in its initial positionalstate. The initialization of the first power transmission unit 61, i.e.,the completion of setting the first power transmission unit 61 in theinitial positional state, is detected by the initialization detector 70.After the first power transmission unit 61 has thus been set in theinitial positional state, the initialization detector 70 is removed fromthe first power transmission unit 61, and then the second powertransmission unit 63 is connected to the first power transmission unit61 to interlock a working unit 10 with the drive unit 50.

The initialization detector 70, which is capable of being detachablyconnected to the first power transmission unit 61, does not need to bekept connected to the first power transmission unit 61. Thus, the firstpower transmission unit 63 can be set in the initial positional stateeven if the operation of the medical manipulator 1 is stopped abnormallyand the first power transmission unit 61 interlocked with the drive unit50 is not stopped in the initial positional state. Therefore, themedical manipulator 1 can be restored to its initial state even if thesame is stopped abnormally, for example, in an emergency. The medicalmanipulator 1 does not need any origin sensor, can be formed in a small,lightweight structure and is excellent in operability. The medicalmanipulator is safe because the initialization detector 70 can beconnected to and disconnected from the first power transmission unit 61even in an emergency during a surgical operation without causing harm tothe subject.

A manipulator stopping procedure for normally ending the operation ofthe medical manipulator 1 will be described. The manipulator stoppingprocedure stops the operation of the medical manipulator 1 only when thejoints of the medical manipulator 1 are set in their initial positionalstates (initial positions). The manipulator stopping procedure will bedescribed with reference to FIG. 12. A control unit 40 that controls apower transmission mechanism 60 on the basis of instructions given by anoperating unit 20 carries out the manipulator stopping procedure to seta part, connected to the second power transmission unit 63, of the firstpower transmission unit 61 at a predetermined initial position.

Thus, the operation of the medical manipulator 1 can normally be stoppedonly when the first power transmission unit 61 is set in its initialpositional state (initial position). The first power transmission unit61 can be restored to the initial positional state when the working unit10 disconnected from the drive unit 50, cleaned and sterilized isconnected again to the drive unit 50. Therefore, the medical manipulator1 can be used immediately after the same has been connected to a powersource without requiring any return-to-origin operation. Thus,troublesome work in a tense situation of surgical operation can beavoided and thereby the efficiency of the surgical operation canremarkably be improved.

In carrying out the following manipulator stopping procedure, thepositional states of the joints are detected by incremental encoderscombined with the joints and any origin sensors, such as absoluteencoders, are not necessary.

A manipulator system comprises the medical manipulator 1, and thecontrol unit 40 for controlling the drive unit 50 of the medicalmanipulator 1. Referring to FIG. 12, the control unit 40 is initialized,a control program for controlling the medical manipulator 1 is started,and the medical manipulator 1 is set in a waiting state upon theconnection of the manipulator system to a power source. When themanipulator system is set in the waiting state, the output shafts of themotors of the drive unit 50 are kept at the initial angular positions orcurrent supply to the motors is inhibited, and the working unit 10 isheld in an initial state. The controller 40 monitors instructionsprovided by the operating unit 20 periodically. The operator operatesswitches included in the control unit 40 and the operating unit 20, andfoot switches and/or a keyboard connected to the manipulator system toprovide instructions. The operator may give instructions by means ofvoice input means or pictorial means. A decision is made as to which oneof an operation start instruction, a return-to-origin instruction and anoperation stop instruction is given in an instruction decision step I,and the operating mode of the medical manipulator 1 is determinedaccording to the instruction. The return-to-origin instruction and areturn-to-origin operation are not those that controls an origin sensorto reset the origin sensor, but those that sets the joints in theinitial positional states, respectively. In an operational statespecified by the operation start instruction, the positional conditionof the working unit 10 follows that of the operating unit 20. Theoperation stop instruction and the return-to-origin instruction aremonitored, and the operating mode of the medical manipulator 1 isdetermined according to the instruction.

When the operation stop instruction is given, the medical manipulator 1stops in a positional state in which the medical manipulator is set atthe time when the operation stop instruction is given, and stays in awaiting state. The return-to-origin operation that is performed when thereturn-to-origin instruction is given operates the motors of the driveunit 50 so as to set the working unit 10 of the medical manipulator 1 inits initial positional state (initial position). After the working unit10 has been set in the initial positional state, the medical manipulator1 stays in the waiting state.

If it is decided that the operation stop instruction is given in theinstruction decision step I, a query is made to see whether or not anoperation ending operation is to be executed. The control unit 40 iscapable of storing data on the variation of the operating mode of themedical manipulator 1 and is capable of deciding an operating state fromwhich the medical manipulator 1 changed to the waiting state. If themedical manipulator 1 is in the return-to-origin operation immediatelybefore the operating state changes into the waiting state, it is decidedthat the return-to-origin operation has been completed before theoperation stop instruction is given, and an operation end operation isexecuted. If the medical manipulator 1 is in the operation end operationimmediately before the state changes into the waiting state and themedical manipulator 1 is not in the return-to-origin operation, it isdecided that the return-to-origin operation has not been completedbefore the operation stop instruction is given, and that the operationend operation is not executed.

Although the operation start instruction, the return-to-origininstruction and the operation stop instruction are used, the controlunit 40 is capable of storing data on the variation of the operatingmode of the medical manipulator 1 and is capable of deciding anoperating state from which the medical manipulator 1 changed to thewaiting state. Therefore, the operation of the manipulator system can beended only when the medical manipulator 1 is in the initial positionalstate. The manipulator system may be controlled by any suitable controlprocedure other than hat shown in FIG. 12, provided that the controlprocedure is capable of ending the operation of the medical manipulator1 normally.

When the manipulator system is thus constructed, the operator is able torecognize the abnormal state of the working unit 10 before starting theoperation of the medical manipulator 1. If the working unit 10 is not inthe initial positional state when the working unit 10 is interlockedwith the drive unit 50, the operator is able to recognize such anabnormal condition of the working unit 10 easily. Possible causes thatset the working unit 10 in a positional state other than the initialpositional state are the abnormal end of the operation of the medicalmanipulator 1 due to emergency or such in the preceding surgicaloperation, and abnormal or incorrect connection of the powertransmitting devices 64, 65 and 66 to the second power transmission unit63 including faulty fastening of the wires, excessive elongation of thewires and such. A condition where the first power transmission unit 61is not stopped in the initial positional state due to the emergency stopof the medical manipulator in the preceding surgical operation can becorrected. Therefore, basic causes of setting the working unit 10 in apositional state other than the initial positional state is the abnormalor incorrect connection of the power transmitting devices 64, 65 and 66to the second power transmission unit 63. Thus, the operator is able torecognize the abnormal condition of the working unit 10 beforehand and,therefore, the medical manipulator 1 is safe.

Basically, it is impossible to restore the first power transmission unit61 joined to the drive unit 50 to the initial positional state ininterlocking the working unit 10 with the drive unit 50 when the medicalmanipulator 1 is stopped abnormally due to emergency during a surgicaloperation. However, in the medical manipulator 1 in the secondembodiment of the present invention, the initialization detector 70provided with an origin sensor can be detachably connected to the firstpower transmission unit 61 after the first power transmission unit 61has been disconnected from the second power transmission unit 63. Theinitialization detector 70 is connected to the first power transmissionunit 61, and the motors of the drive unit 50 are actuated to set thefirst power transmission unit 61 in its initial positional state. Sincethe first power transmission unit 61 can be set in the initialpositional state beforehand, the troublesome return-to-origin operationdoes not need to be performed during a surgical operation. In a statewhere the initializing operation for setting the first powertransmission unit 61 interlocked with the drive unit 50 in the initialpositional state has been completed, the working unit 10 and the secondpower transmission unit 63 can be set in their initial positional statesby connecting the second power transmission unit 63 interlocked with theworking unit 10 to the first power transmission unit 61 interlocked withthe drive unit 50. Thus, the medical manipulator 1 does not need anypermanent, built-in origin sensor, can be formed in a small, lightweightstructure and is excellent in operability.

If the medical manipulator 1 should be stopped for an emergency stop dueto an emergency, the medical manipulator 1 must safely be retracted andremoved from the subject without arming the subject. The medicalmanipulator 1 enables the disconnection of the first power transmissionunit 61 interlocked with the drive unit 50 from the second powertransmission unit 63 interlocked with the working unit 10 in a statewhere the working unit 10 is inserted in a part of the subject's body.It is possible that the working unit 10 harms the subject if the workingunit 10 inserted in a part of the subject's body is moved inadvertently.The first power transmission unit 61 interlocked with the drive unit 50can safely be disconnected from the second power transmission unit 63with the working unit 10 held immovably. Since the drive unit 10 caneasily be driven, the drive unit 10 can be set in a safe position byoperating the unit drive 10 by, for example, another pair of forceps, ifthe working unit 10 is in a dangerous position. The drive unit 10 can beextracted through the tracheal tube even if the drive unit 10 is notrestored to its reference position. If the surgical operation isinterrupted when there is something wrong in the power transmittingdevices, the components and structural members of the mechanism on theside of the working unit 10 and the mechanisms on the side of the driveunit 50 are perfectly controllable, the manipulator system can simplyand quickly be set to rights without requiring troublesome operationsfor initializing and starting the manipulator system at all simply byreplacing the defective working unit 10 with a new one and connectingthe second power transmission unit 63 interlocked with the working unit10 to the first power transmission unit 61 interlocked with the driveunit 50. If the initial positional state of the drive unit 50 is notpreserved due to the abnormal end of the operation of the medicalmanipulator 1, the drive unit 50 can be restored to its initialpositional state by using the initialization detector 70.

As apparent from the foregoing description, according to the presentinvention, the working unit can be cleaned and sterilized, areturn-to-origin operation can be carried out without using any absoluteencoders or origin sensors, and the working unit can always be set inits initial state before and after connecting the working unit to anddisconnecting the same from the drive unit, the medical manipulator canbe formed in a small, lightweight structure, and has an improvedoperability because the first power transmission unit and the secondpower transmission unit can detachably be connected, and the first powertransmission unit is capable of exerting a back drive torque sufficientfor locating the second power transmission unit such that the first andthe second power transmission unit are connected in the same positionalrelationship as a predetermined positional relationship in which thefirst and the second power transmission unit had been connected beforethe same were separated from each other.

Since the control unit sets the first power transmission unit in thepredetermined initial positional state after the normal completion of anoperation, the medical manipulator can necessarily be restored to theinitial positional state when the work unit is interlocked again withthe drive unit after disengaging the work unit from the drive unit,cleaning and sterilizing the work unit after the completion of asurgical operation. Thus, the medical manipulator can be usedimmediately after the connection of the same to the power source withoutrequiring a troublesome return-to-origin operation. Thus, troublesomework in a tense situation of surgical operation can be avoided andthereby the efficiency of the surgical operation can remarkably beimproved.

Since the initialization detecting means is capable of being detachablyconnected to the first power transmission unit, the initialization ofthe drive unit can be detected without permanently mounting theinitialization detecting means on the first power transmission unit, andthe return-to-origin operation is possible even in a state where theoperation is ended abnormally. Since the medical manipulator does notneed to be provided with any origin sensor, the medical manipulator canbe formed in a small, lightweight structure and has an improvedoperability. Furthermore, the medical manipulator is safe because theinitialization detector can easily be connected to and disconnected fromthe first power transmission unit even in an emergency during a surgicaloperation without causing harm to the subject.

Although the invention has been described in its preferred embodimentwith a certain degree of particularity, obviously many changes andvariations are possible therein. It is therefore to be understood thatthe present invention may be practiced otherwise than as specificallydescribed herein without departing from the scope and spirit thereof.

1. A medical manipulator comprising: a working unit that performsoperations; a drive unit that drives the working unit on the basis ofinstructions given thereto by an operating unit; and a powertransmission mechanism for transmitting driving force of the drive unitto the working unit; wherein the power transmission mechanism includes afirst power transmission unit interlocked with the drive unit, and asecond power transmission unit interlocked with the working unit andcapable of being detachably connected to the first power transmissionunit, and a back drive torque of the first power transmission unit islarger than a drive torque of the second power transmission unit.
 2. Themedical manipulator according to claim 1, wherein the back drive torqueof the first power transmission unit has a strength more than 0.05N·mwhen the first and the second power transmission unit are connectedtogether.
 3. The medical manipulator according to claim 1, wherein theoperating unit that generates instructions, wherein the working unit andthe second power transmission unit are integrated in an assembly, theoperating unit and the first power transmission unit are integrated inan assembly, and the assembly of the working unit and the second powertransmission unit, and the assembly of the operating unit and the firstpower transmission unit can detachably connected together.
 4. A methodof using the medical manipulator according to claim 1 when the medicalmanipulator is stopped in an emergency in a state where the working unitis inserted in a cavity of a surgical subject, said method comprisingthe steps of: removing at least the drive unit and the first powertransmission unit; and extracting the working unit and the second powertransmission unit from the cavity of the surgical subject.
 5. A methodof using the medical manipulator according to claim 1 when the medicalmanipulator is stopped in an emergency in a state where the working unitis inserted in a cavity of a surgical subject, said method comprisingthe steps of: removing at least the drive unit and the first powertransmission unit; setting the working unit in a safe position bymanually operating the second power transmission unit; and extractingthe working unit and the second power transmission unit from the cavityof the surgical subject.
 6. A method of using the medical manipulatoraccording to claim 1 when the medical manipulator is stopped in anemergency in a state where the working unit is inserted in a cavity of asurgical subject, said method comprising the steps of: removing at leastthe drive unit and the first power transmission unit; and setting theworking unit in a safe position by manually operating the working unitusing a forceps; and extracting the working unit and the second powertransmission unit from a cavity of a surgical subject.